drm/i915: split out intel_display_reg_defs.h

Split out the display register helper macros to a separate file. For
now, include it from i915_reg.h, but note that there are already files
that don't need i915_reg.h, such as intel_audio.c.

Cc: Lucas De Marchi <lucas.demarchi@intel.com>
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/3af47193ff5219b6d2cfe353b752ec4bb44de4f1.1668008071.git.jani.nikula@intel.com

drm/i915: move mipi_mmio_base to display.dsi

Move display DSI related members under drm_i915_private display
sub-struct.

Prefer adding anonymous sub-structs even for single members that aren't
our own structs.

Abstract mmio base member access in register definitions in a macro.

Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Reviewed-by: Lucas De Marchi <lucas.demarchi@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/dc7c5a871fe558a809ea943eca5c71dfff1740a8.1661779055.git.jani.nikula@intel.com

drm/i915/reg: split out vlv_dsi_regs.h and vlv_dsi_pll_regs.h

The VLV (including CHV, BXT, and GLK) DSI registers have fairly isolated
usage. Split the register macros to separated files.

Cc: Matt Roper <matthew.d.roper@intel.com>
Reviewed-by: Matt Roper <matthew.d.roper@intel.com>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20220217224023.3994777-3-jani.nikula@intel.com